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I am trying to build a laminar flow box using instructions at these YouTube links for design and build.

They recommended getting a Dayton squirrel cage air blower model 1TDU2 rated at 1202 CFM. The performance sheet for this air blower ( CFM vs. in wg) can be seen at this link I've already purchased this... (can be returned)

I am now considering buying one of these HEPA filters from Ebay:

A. CAMFIL FARR. 855023669, PX-21.75-44.00-9-40-FU-00-00-0 MEGALAM PANEL HEPA FILTER (link) = 0.40 in W.G. / 100FPM / 554CFM

B. CAMFIL FARR 85502A548 MEGALAM PANEL P7-23.12-47.12-5-08-00-7D-00-0 (link) = 0.58 in W.G. / 100FPM / 704CFM

C. CAMFIL FARR 855024774 MEGALAM PANEL P7-18.00-48.00-2-03-SR-00-00-0 PACK OF 2 (link) = 0.71 in W.G. / 105FPM / 550CFM

My requirement for maintaining microbial sterility are

(i) minimum 90 FPM

(ii) minimum 99.99% air purity

The help I seek is in the form of your answers to my questions below, please:

I know there is a large mismatch between air blower CFM rating and any of these filters recommended CFM rating.

1. Are any of the filters listed above matched with my air blower in terms of CFM rating? I guess not, but I want to be sure.

2. Is matching of the air blower CFM and filter CFM done at zero pressure, or operating pressure drop water gauge (which varies across these 3 filters) ?

3. FYI, I will be using a pre-filter to get rid of large particulate matter, that contributes additionally 0.3 in WG pressure drop

4. If at total WG pressure drop, the air blower CFM is X, and the rated air filter CFM is Y, then for maintaining filter integrity, I know X < Y and X = Y is OK (where X > 90FPM). But how high can X get when X > Y ? 20% , 30% , 100% - something else?

5. What are the consequences of X >> Y ? Will it blow out the HEPA filter? And more air means exceeding capacity to capture particles, so more air, but partially dirty air, right?

6. Can anyone help me with who to read and interpret a Camfil Farr HEPA filter's label, especially the description e.g. PX-21.75-44.00-9-40-FU-00-00-0, P7-23.12-47.12-5-08-00-7D-00-0, P7-18.00-48.00-2-03-SR-00-00-0 etc.?

7. I was told that for my application, a "high flow" (~1000 CFM) thicker HEPA filter (11 5/8 in) is better than a "standard" thinner one (5 7/8 in) with only ~ 500 CFM. Is this a valid piece of advice, given my goals?

8. From Ebay or elsewhere, do forum users have friendly advice for a (an equally or more) cost effective alternative to these Camfil Farr HEPA filters?

Thanks, in advance. Have a great weekend!

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  • $\begingroup$ Possible duplicate : engineering.stackexchange.com/q/2390/10902 $\endgroup$ – Solar Mike Jul 27 '19 at 5:15
  • $\begingroup$ No it's not.... please read both contents carefully in this case, and responsibly post any comments that may reduce or eliminate the possibility of a response. This is not cross-posted, nor is it redundant or duplicated. I request you to change or delete your comment...And I will too. Thanks! $\endgroup$ – Tom de Medts Jul 27 '19 at 15:36
  • $\begingroup$ "possible".... and the Q I link to has the expression to calculate the pressure drop AND to approximate the fan curve... $\endgroup$ – Solar Mike Jul 27 '19 at 15:44
  • $\begingroup$ I already have the fan curve from the manufacturer website. And know the delta pressure curve for the HEPA filter from Camfil Farr's tech people. My questions are different. I did notice use of "possible" but you continue to ignore the context of my questions, and the much wider range and number of questions asked. So I will no longer dignify your comments with a response. $\endgroup$ – Tom de Medts Jul 27 '19 at 19:01

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